With a median surface water temperature of 28.71 degrees recorded on July 24, the Mediterranean Sea set its new record that day. A statistical formality for this region which is warming 20% faster than the rest of the world and which has concentrated 86% of global carbon dioxide emissions over the last decade, according to a United Nations report and an opportunity for certain species who see its warmer waters as a new playground.
“We have counted 1,000 new species in the Mediterranean, from all groups: fish, obviously, but also echinoderms [la famille des étoiles de mer]molluscs, algae and crabs,” confirms Christine Pergent, professor emeritus at the Pascal-Paoli University of Corsica and host of the Alien network, which compiles observations of invasive exotic species in the Mediterranean.
An open sea at every window
And there are multiple entry points: There is the natural entrance to the Strait of Gibraltar through which the species that were supposed to come to the Mediterranean did so a long time ago. There is the most recent opening of the Suez Canal (in 1869) which linked the waters of the Mediterranean and the Red Sea. Finally, there are the arrivals of species permitted “by anthropogenic parameters. Transported by the ballast waters of ships, as probably for the blue crab, or landed by pure accident like the taxifolia, an algae originally from Australia “escape“ aquariums of Monaco “.
“We must differentiate between exotic species, which we call “alien”, therefore, because they are truly foreign, arriving without there being any continuity with their original geographical area, from species like the grouper or the barracuda, first confined to the Red Sea and the eastern Mediterranean basin before arriving on our western coasts and which simply extended their initial area by finding more favorable conditions,” specifies the biologist.
Soon the Marseille fugu
Certain species present real economic and taste opportunities, like the blue crab which, with a respectable size of around fifteen centimeters, has come to fill “the lack” of large crabs in the Mediterranean, as Christine Pergent explains. “An entire economic sector has developed in Turkey around this crab originating from southern Canada and which certain Corsican restaurants now put on their menu. » But conversely others pose a problem: “There is the puffer fish, toxic like the fugu, which is therefore difficult to cook, the lion fish, also, which looks like a capon [rascasse rouge qui peut atteindre les 50 cm] and is extremely voracious and creates imbalances. »
New species that are difficult to capture
In this great ecological upheaval, there can also be draws. “We can say for example that the flute fish, native to tropical or subtropical regions and which plays the same role as the capon, will replace it, but with what consequences, since they do not eat the same algae? » A question that is repeated for rabbitfish, from the Pacific, and which competes with Mediterranean sauce.
An evolution of Mediterranean biodiversity which has not escaped Gérard Carrodano, a professional fisherman and diver based in La Ciotat, a stone’s throw from Marseille. While he is delighted with the maintenance and reproduction of barracuda or grouper in our waters, “species at the top of the food chain which therefore find something to eat – a good indicator”, he observes that the outlets for these new fish are not yet developed, in addition to the difficulty of catching them.
“To fish for barracuda, an excellent fish, you need fairly fragile nets that are very high above the water, which is not possible here with all the maritime traffic, especially in summer. Also, there aren’t enough of them yet, and I can gain 30 or 40 kg one day and nothing the next day. I therefore cannot supply a sector if I am asked to do so,” illustrates the fisherman who regrets other inconveniences such as the multiplication of jellyfish or the scarcity of sea urchins and octopuses.
Our 20 Minutes Under the Sea file
“While we need to educate consumers so that they taste and appreciate these new species, there are plenty of them that are not edible and have no natural predators. The problem is that we don’t really have a solution to fight against them apart from preventive actions such as installing filters on the ballasts, or deballasting ships before they enter a new area”, returns Christine Pergent. But with the intensification of trade – 30% of global container trade passes through the Suez Canal – and climate change, “we will continue to favor species from the Red Sea and the South Atlantic. This is why we are talking about a tropicalization of the Mediterranean,” concludes the researcher.